Microscopic electromagnetic radiation transmitter or detector

ABSTRACT

The present invention relates to a microscopic electromagnetic radiation transmitter or detector and a so-called near-field probe (1) whose body takes the form of a polyhedron point and consists of a material which is at least partially permeable to electromagnetic radiation in the spectral region used. The polyhedron point is delimited by an imaginary base surface beyond which the substantial part of the body is continued to form a total probe body, which is not defined in greater detail. The polyhedron point has &#34;n &#34; side faces and edges leading to an acute point (2) are formed between adjacent side faces. According to the invention, at least two side faces of the body of the polyhedron probe (1) are coated with thin, electrically conductive layers which absorb some of the electromagnetic radiation in the spectral region used, preferably consist of materials such as aluminum, gold or silver and are less than 0.2 μm thick. The front part of the polyhedron point (2) is also coated with the material used, resulting in an efficient near field probe with comparatively high resolution in optical near field scanning microscopy, simultaneous scanning tunnel microscopy also being possible with the same point.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a microscopic transmitter or detectorof electromagnetic radiation which, hereinafter, is referred to as anear-field probe (1), the body of which has the form of a polyhedronpoint and consists of a material that is at least partially permeable toelectromagnetic radiation in the spectral range used, whereby thepolyhedron point is delimited by an imaginary base surface beyond whichthe substantial part of the body is continued to form a total body ofthe probe not defined in greater detail, said polyhydron point having "n" side faces in a way such that sharp edges are formed between adjacentside surfaces, such edges leading to an acute point, whereby the pointof the near-field probe serves as an almost point-like source foremitting electromagnetic radiation into the external space of the probe,or as an almost point-like receiver for the penetration ofelectromagnetic fields into the interior of the near-field probe,whereby at least two side surfaces of the body of the polyhedron probeare coated with thin, electrically conductive layers, the latterpartially absorbing the electromagnetic radiation in the spectral rangeused, and preferably consisting of material such as aluminum, gold orsilver and having a thickness of less than 0.2 μm.

2. The Prior Art

Known probes of the above type have the property that is important totheir sensor function, which is that an aperture is mounted on the pointin a metal film. Said known probes include:

(a) the probes of Pohl (D. W. Pohl, W. Denk, M. Lanz 1984! Appl. Phys.Lett. 44, 651-653), consisting of a glass or quartz fiber ending in apoint, such fiber being coated with metal in such a way that an apertureis available on the point in the metal coating.

(b) The probe of Betzig et al (E. Betzig, J. K. Trautman, T. D. Harris,J. S. Weiner, R. L. Kostelak 1991!; Science Vol. 251, 1468-1470), which,in a way very similar to the one of Pohl et al, consists of glass fibercoated with metal and ending in a point, the metal coating of said fiberhaving a submicroscopic aperture on the point. Because of the aperturein the metal coating, the front part of the point is uncoated. Saidprobes have the drawback that the complex structure of an aperture in ametal film directly on the point limits the minimum dimensions of thepoint to about 0.1 μm, whereby the aperture must not be smaller thanabout 15 nm. Therefore, it has to be expected that with the resolutionof 13 nm achieved, the limit of the resolving capacity of the scanningnear field optical microscopy SNOM (Scanning Near Field OpticalMicroscopy) has been reached with such points. At the same time, thewidth of the point of at least 0.1 μm conditions that the aperture canbe brought close to the surface to a distance of less than 15 nm only inexceptional cases, such distance being required for obtaining theresolution of 15 nm.

The tetrahedron probe described by Danzebrink and Fischer, which isspecified in application DE 43 29 985 A1, has the same drawback.However, versus the probes described above in (a) and (b), said probehas the advantage that it satisfies the function of the transmissionelement in a superior way.

Since the aperture satisfies the function of the SNOM-probe in bothcases, said probe not being electrically conductive everywhere, asimultaneous SNOM and scanning tunnelling microscopy with high lateralresolution is not possible with the identical point in said cases.

SUMMARY OF THE INVENTION

The invention is based on the problem of creating an efficientnear-field probe with which a resolution as high as possible can beachieved in scanning near-field optical microscopy, and which permitssimultaneous scanning tunnelling microscopy with the same point.

The solution of said problem is obtained according to the invention inthat also the most frontal part of the polyhedron point is coated withthe coating material used. Said device has the advantage that theresolution of a near-field microscope equipped with said probe is nolonger limited by the aperture because the most frontal part of thepoint itself serves as the emitter or receiver of electromagneticfields. Furthermore, since the most frontal part of the point is coatedwith an electrically conductive material, the near-field probe can beused both in optical near-field microscopy with high resolution and atthe same time also in scanning tunnelling microscopy.

The developments of the idea of the invention described in the dependentclaims contain additional advantages.

Further benefits and features of the invention become clear from thefollowing specification of a number of preferred exemplified embodimentswith reference to the attached illustrations, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of the polyhedron probe;

FIGS. 2A and 2B show a schematic representation of the arrangements ofthe polyhedron probe in an optical near-field microscope;

FIG. 3 shows a schematic representation relating to the coating of thepolyhedron probe by rotation evaporation coating;

FIG. 4 shows a schematic representation relating to the coating of thepolyhedron probe with an uncoated edge;

FIG. 5 shows an inverse dark-field collector for inverse photontunnelling microscopy;

FIG. 6 shows a measured dependence of the near-field signal on thespacing in an inverse photon tunnel microscope; the intensity of thenear-field signal is plotted on the ordinate and the relative spacingbetween the point (2) and the object (6) is plotted on the abscissa; theabsolute spacing is not known;

FIG. 7 shows a scanning force-microscopic image of the test object;

FIG. 8 shows an image of the test object with an inverse photontunnelling microscope with a tetrahedron point having the design 1;

FIG. 9 shows a reflection arrangement with irradiation of the point fromthe outside; and

FIG. 10 shows a reflected-light type reflection arrangement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In connection with known arrangements of scanning near-field opticalmicroscopy SNOM (Scanning Near-Field Optical Microscopy), a point 2 withsubmicroscopic dimensions that are smaller than the wavelength of theelectromagnetic radiation used, in the arrangement I (FIG. 2A) serves asa submicroscopic transmission antenna, and in the arrangement II as areceiving antenna. In the arrangement I, light emitted from a lightsource 5 is transmitted onto the near field probe 1 via a transmissionelement 4. The transmission member 4 may be a wave conductor such as,for example a glass fiber, or an optical radiation path with lenses, oralso a combination of a number of such components. An additionaltransmission element 3 serves for transmitting light energy from thetransmission element 4 to the point 2. The transmission element 3 alsoserves the purpose of transmitting to the point 2 light from a regionwith dimensions that are large versus or comparable to the wavelength ofthe light, such a point having dimensions that are small as compared tothe wavelength. The transmission element 3 and the point 2 are theessential components characteristic of the design of a near-fieldmicroscope. Said components form the near-field probe 1. The point 2 ismounted within the direct proximity of the surface of the object 6,which is supported by an object support 7. A displacement device 10serves the purpose of displacing the object in three dimensions relativeto the point. Light reflected by the object 6 is transmitted by atransmission element 8 to the detector 9, which serves the purpose ofconverting the signal received into an electrical signal, which is thenear field signal, which is processed further as the signal for theoptical near-field microscopy. In the arrangement II (FIG. 2B) with thepoint 2 serving as the receiving antenna, the positions of the source 5and the detector 9 are exchanged. If the source 5 and the detector 9 andthe associated paths of energy transmission to the point 2 or the object6 are arranged on opposite sides of the object 6 as shown in FIG. 2,such an arrangement is called a transmission arrangement. If saidcomponents are mounted on the same side of the object, such anarrangement is called a reflection arrangement. In optical near-fieldmicroscopy, use is made of the fact that the object 6 has a retroactiveeffect on the emission or absorption of the probe 1 within the immediateproximity of the point 2, i.e., within the range of the near field ofthe probe, so that the signal (optical near field signal) received bythe detector 9 is a characteristic function of the spacing between thepoint 2 and the surface of the object, and also of the local opticalproperties of the surface of object 6. The point 2 is guided across thesurface of the object 6 with a spacing ranging from half of thewavelength to less than one nm. The optical near-field microscopy wasdemonstrated in a number of different versions, which substantiallydiffer from each other on account of the type of probes 1 used and thearrangements of the probes for the microscopic procedure, i.e., onaccount of the type and arrangement of the transmission elements 3, 4and 8 for the routes of energy transmission between the point 2 and thedetector 9, on the one hand, and between the source 5 and the point 2 onthe other hand.

A probe according to the invention may have the shape shown in FIG. 1for the case of the tetrahedron point (n=3), which is a polyhedronleading to a point 2 and made of a transparent material. The sidesurfaces P_(j) (j=1, . . . , n) are coated with thin films of anelectrically conductive material partially absorbing the electromagneticradiation such as, for example, an electrically conductive metal, in away such that the part of point 2 projecting farthest consists of thecoating material. The edges K_(ik) between the coated surfaces P_(i) andP_(k) may be uncoated or coated with the coating material as well.Uncoated edges may serve the function of transmitting electromagneticenergy from macroscopic dimensions into the microscopic range of thepoint 2, as described already earlier in laid-open specification (DE 4329 985 A1). They have the function of the transmission element 3 in FIG.2. Furthermore, it is possible to coat only two of the side surfacesP_(j) (j=1, . . . , n) and the part of point 2 projecting farthest,whereby the edge K_(ik) between the two coated side surfaces P_(j) (j=1,. . . , n) may be coated or uncoated.

The design of the base surface P_(o) remote from the point is left open,said surface may be, for example a ground surface, but it also may be animaginary separation surface for continuing the polyhedron to form asuitable body of any desired dimension.

The transparent material of the body of the near-field probe may be atransparent amorphous glass, but also transparent crystalline materialsuch as diamond, quartz, saphire, or also silicone for the infraredspectral range. Also, it may be material with higher nonlinearsusceptibilities such as, for example lithium niobate, orphotoluminescent material such as, for example doped glasses orcrystals. The material must not necessarily be homogeneous andisotropic. The surface of the body or cutouts of the surfaces of thebody may be provided with a thin layer of another refractive index, witha contamination layer, a doping layer, or with a thin coating consistingof another material.

The body K of such near-field probes can be manufactured in all sorts ofdifferent ways. A few manufacturing processes are described in thefollowing. If amorphous or polycrystalline materials such as, forexample glass are used, fractions can be produced in differentdirections. By fracturing a glass body several times it is possible, forexample to produce a tetrahedron point. Said method of fracturing forproducing the body of polyhedron probes is applicable to other materialsas well, in particular also to crystalline materials, in which fracturesare preferably produced along selected crystal planes. By controlledslight cutting and splitting along said planes it is possible to producevery exact edges and, if need be, corners.

Furthermore, it is possible to produce such edges and surfaces bygrinding, polishing and etching methods as well.

Furthermore, it is possible to produce such points by microlithographicmethods, as it is known, for example in the case of silicone points,which are transparent in the infrared spectral range.

The side surfaces P_(j) (j=1, . . . , n) may be coated with a thin filmof a coating material, which may be applied by sputtering or thermalevaporation, or also by other methods. Coating may be carried out, forexample by rotation vapor deposition, in which process the polyhedronpoint rotates during vapor deposition around the axis 11 extendingthrough the point. Said rotary axis 11 is inclined relative to the vaporjet by an angle 12 smaller than 90°, as shown in FIG. 3, whereby theangle 12 may be varied during the coating process. On this way, thepoint and all side surfaces and all edges between the side surfaces arecoated with metal.

On the other hand, for the case of the tetrahedron point, the coating oftwo adjacent side surfaces P₁ and P₂ can be carried out in two steps, ina way such that the edge K₁₂ remains uncoated or is coated with a layerthickness that is thinner as compared to the coating of the sidesurfaces. The sides are coated successively with a material vapor jetthe direction of which is inclined with an angle 12 smaller than 90°relative to the axis 11 extending through the point, whereby the angle12 is, at the same time, greater than the angle 13 between the edge K₁₂and the axis 11, and its direction is, furthermore, inclined at an angle14 smaller than 90° relative to the axis 15 extending through the edgeK₁₂ (FIG. 4).

Also in case of a polyhedron point with any desired number of sidesurfaces it is possible to carry out the coating process in such a waythat one edge is uncoated whereas all sides, all other edges and thepoint are coated. In this case, coating takes place within the ranges ofangles (12) and (14) specified above, whereby said angles may be variedin the course of the coating process.

In preferred embodiments of the invented polyhedron probe 1, the sharpedges K_(ik) leading to a point, the coatings with the coating materialand the material of the probe satisfy functions that are of significantimportance to the property of such a probe as a submicroscopictransmitter or receiver of light.

Preferred embodiments of the probe and its mode of operation aredescribed in greater detail in the following.

(1) The body of the polyhedron point 1 consists of a material which istransparent for the spectral range of the electromagnetic radiationused. The material of the tetrahedron is a transparent dielectric suchas, for example glass, quartz, saphire or diamond. The coating of allsides P_(i) consists of a thin metal layer such as, for examplealuminum, gold or silver, whereby the edge K₁₂ between the two sides P₁and P₂ is uncoated and the point 2 is coated.

The coatings and the uncoated polyhedron edge K₁₂ between the coatedside surfaces serve the function of the wave conductor structures 3,with the help of which electromagnetic energy can be efficientlytransmitted along the edge to the point 2. An analogy exists between theuncoated edge and the known double-wire wave conductor, which permitsthe transmission of electromagnetic energy along a cross section that issmall as compared to the wavelength. The wave conduction is interruptedby the metallic point 2, from which the electromagnetic energy isreflected.

(2) Polyhedron point 1 made of transparent material, in connection withwhich all sides P_(i) (i=1, . . . , n) and the point 2 are coated withmetal. The semitransparent metal layers and the edges serve fortransmitting electromagnetic energy in the form of surface waves. Thewave conduction is interrupted by the point, from which theelectromagnetic energy is reflected. Surface waves in the form ofsurface plasmonae can be produced on a metal coating by irradiation fromthe inside of the probe 1. With suitable selection of the angle ofincidence of the radiation, exitation of the surface waves takes placerelative to the surface P_(i). In the edges, the conditions ofgenerating surface waves are different from those on the side surfacesdue to the changed geometry. For this reason, with suitable selection ofthe angles of incidence of the irradiation light, the preferred waveconduction can be obtained along the edge structure.

(3) The body of the polyhedron probe 1 consists of photolumineacencingmaterial, or of a material which, in the regions of the surfaceenclosing the point 2, is doped with photoluminescent centers. Thephotoluminescence is stimulated as the light is being transmitted intothe photolumineacent regions. Because of the wave conductor property ofthe edge, the spectrally shifted fluorescence light is transmitted alongone edge to the point 2, from where it is reflected.

(4) The same arrangement as the one in (3) is used in order to produce astimulated emission of the luminescenging centers in the polyhedronpoint at higher irradiation intensities. When selecting known suitableluminescence centers, the stimulated emission leads to laser activity,which can be detected based on a nonlinear increase in the radiationemitted by the point with increasing irradiation intensity.

(5) This embodiment is different from the embodiment 2 or 3 on accountof the fact that the body of the polyhedron probe consists of nonlinearoptical material with high nonlinear optical susceptibilities such as,for example, lithium niobate. At high irradiation intensities,irradiation of the polyhedron point with low-frequency light leads todoubling of the frequency or to frequency division and emission of saidlight from the point, such light being frequency-shifted versus theirradiation light.

The polyhedron points can be used in many different ways as near-fieldprobes for optical near-field microscopy.

(1) With some transmission arrangements, the polyhedron point has thefunction of a submicroscopic transmitter (arrangement I). Stimulation ofthe probe for radiation takes place through irradiation via thetransmission elements 4 and 3, and light emitted by the point 2 is usedas the signal for the near-field microscopy.

(2) With other transmission arrangements, the point 2 of the probe 1 hasthe function of a submicroscopic receiver for light (arrangement II).Exciting of the probe takes place through light, which is emitted fromthe object 6. The energy transmitted from the point 2 via thetransmission elements 3 and 4 serves as the optical near-field signal.

(3) In a specially realized arrangement of the near-field probe in aninverse photon tunnelling microscope (FIG. 5), the near-field-probe Iserves as the transmitter as described for arrangement I. The object 6is adsorbed on a thin, commercially available cover glass serving as thesupport 7. The cover glass is mounted on a dark-field immersioncollector with the help of the immersion oil 18. Said collector forms acomponent of the transmission element 8 in arrangement I. The collectorconsists of a dielectric body 16, which has the form of the segment of arotation paraboloid. Said paraboloid is provided on the side with areflecting layer 17. The uncoated side surface may alternatively serveas the reflecting surface as well. The tetrahedron point 2 is arrangedwithin the focal zone of the parabolic mirror. A circular opaque beamstop 19 is mounted on the outlet surface of the parabolic mirror. Saidbeam stop covers the part of the light transmitted through the collectorthat is reflected from the focal point of the parabolic mirror into thecone, which is limited by the limit angle of the total reflection 20. Animmersion lens can be used instead of the parabolic mirror as well. Thelight transmitted by the collector is received on the detector 9. Saidarrangement with the dark-field immersion collector serves the purposethat light emitted by the point 2 is received on the detector 9 only ifthe tetrahedron point is brought close to the object within the range ofthe evanescent modes of the air/glass interface of the cover glass. Inthis way, a signal is obtained that grows exponentially with thedecrease in the spacing of the tetrahedron point from the cover glass,as shown in FIG. 6. Said signal serves the purpose of adjusting thespacing between the point and the cover glass with the help of anelectronic controller and the adjusting element 10, in a way such that apreset should-be value of the signal is always maintained. For recordinga screen picture, the cover glass is displaced raster-like relative tothe tetrahedron point 1 with the help of the adjusting element 10. Thetrailing of the point in the axial direction, such trailing beingconditioned by the controller, is recorded as the signal for producingthe picture. In this way, pictures of a test object were recorded withthe tetrahedron point of design 1. FIG. 7 shows a picture of the testobject, which was recorded with a force microscope. FIG. 8 shows thenear-field optical recording of the cutout of such a test object. It waspossible to demonstrate in this way that with the tetrahedron point ofdesign 1 having the arrangement described herein it is possible toreproduce for optical near-field microscopy a test object that can berecognized again, with a resolution of approximately 30 nm. Resolutionsof 15 nm with the optical near field have been reported earlier;however, these did not involve structures that can be recognized again,so that it is not clear whether these structure details in factrepresent a genuine reproduction of detail structures of the object.

(4) In connection with the special arrangement of the inverse photontunnel microscope introduced here, the above-described arrangement ismodified to the extent that the cover glass 7 is coated with an almostopaque metal layer of silver or gold, and that the object 6 is adsorbedon said metal layer. Light emitted by the near-field probe 1 does notpenetrate into the collector through the metal film at spacings of thepoint from the object that are greater than one wavelength of the light.Only if the point is brought close to the object with spacings withinthe range of the wavelength, local surface plasmonas are stimulatedwithin the zone of the point 2 and the oppositely disposed metal layeron the cover glass 7 when a suitable wavelength of the irradiation lightis selected. Such surface plasmonas lead to stimulation of delocalizedsurface plasmonas in the metal layer, which in turn lead to reflectionof light by the collector. In this way, a signal of the lighttransmitted by the collector is obtained that varies with the spacing,which signal is used for the inverse photon tunnel microscopy. Saidarrangement has the property that the resonant plasmona stimulation ishighly influenced by the refractive index of the object 6 in the gapbetween the point 2 and the metal layer (on support 7), and that forthis reason it is possible to achieve a very high contrast of thenear-field signal for slight variations of the refractive index of theobject 6.

(5) Reflection arrangements.

Reflection arrangements for optical near-field microscopy expand theapplicability of optical near-field microscopy to nontransparent objects(6). Two special reflection arrangements for optical near-fieldmicroscopy with the polyhedron point are explained in the following.

(a) (FIG. 9) - The point 2 is irradiated from a light source 5 through afocusing transmission element 8, so that the beam of light is focusedfrom the outside in the gap between the point 1 and the object 6 to arange of an edge K_(ik) that reaches up to the point 2, or ends a fewμm's from the latter. The light, which is reflected from the point intothe polyhedron point and exits from the base surface P_(o), is directedwith the help of a microscope lens 4 at a detector 9 in the image planeof the lens, whereby the lens is adjusted in such a way that the point 2is disposed in the plane of the lens.

(b) In a reflected-light reflection arrangement (FIG. 10), thepolyhedron point 1 is irradiated from a light source 5 through atransmission element 4, 8, for example a microscope lens, in such a waythat a focused beam is focused through the base surface P_(o) on a zoneof an edge K_(ik) reaching up to the point 2 or ending a few μm's fromthe point. The light scattered back from the point 2 into the polyhedronpoint 3 and exiting through the base surface P_(o) is directed at thedetector with the help of the transmission element 4, 8.

(6) Arrangements for simultaneous SNOM and STM.

The near-field probe 1 is operated in any desired arrangement of opticalnear-field microscopy. A wire is contacted by way of an electricallyconductive connection with the metal coating of the polyhedron point 1.Also, an electrically conductive site of the object is contacted with anelectrical line. As commonly done in scanning tunnelling microscopy, atunnel voltage is applied between the two electrical connections and thecurrent is measured. Simultaneous; STM and SNOM can be realized indifferent ways. For example, in common STM, the current signal can beused for controlling the spacing between the point and the object. Thefollow-up signal is registered as the STM-signal for producing thepicture. The optical signal is recorded as the signal for simultaneousoptical near-field microscopy. Alternatively, the optical near-fieldsignal can be used as described above for controlling the spacing,whereas the current signal is recorded as the STM-signal.

The arrangement 6 can be used also for testing light-induced influenceson the tunnel current. Versus earlier arrangements for testinglight-induced influences on the tunnel current (L. Arnold et al, Appl.Phys. Lett. 51, page 786; 1987), said arrangements offer the decisiveadvantage that irradiation of the object takes place only within a zonelimited by the near-field probe, i.e., within a zone that is muchSmaller than a zone irradiated through focusing.

The near-field probes can be used not only as probes for scanningnear-field optical microscopy. They are generally usable as probes whenmeasurement of local and also time-dependent optical properties isinvolved, such as measurement of the spatial distribution ofelectromagnetic radiation fields or near fields, measurement oftime-dependent intensity variations in very small ranges, andmeasurement of the point transmission function of optical systems byarranging the emitting near-field probe in an inlet plane of the systemas a point-like light source and measuring the intensity in another siteas a function of the arrangement of the emitting probe.

I claim:
 1. Microscopic transmitter or detector of electromagneticradiation, which is near-field probe, comprisinga body K having the formof a polyhedron point and comprising a material at least partiallypermeable to electromagnetic radiation in the spectral range used,whereby the polyhedron point is delimited by an imaginary base surfaceP_(o) and continued beyond a substantial part of the body K to form atotal body of the probe not defined in greater detail, and has "n" sidesurfaces P_(j) (j=1, . . . , n), in a way such that sharp edges K_(ik)are formed between adjacent side surfaces P_(i) and P_(k), such edgesleading to an acute point; said acute point of the near-field probeserves as an almost point-like source for the emission ofelectromagnetic radiation into the external space of the probe, or as analmost point-like receiver for the penetration of electromagnetic fieldsinto the interior of the near-field probe; at least two side surfacesP_(j) (i=1, . . . , n) of the body K of the polyhedron probe are coatedwith thin electrically conductive layers partially absorbing theelectromagnetic radiation in the special range used, said layersselected from the group consisting of aluminum, gold and silver andhaving a thickness of less than 0.2 μm; and the most frontal part of thepolyhedron point is coated with the material used.
 2. Near-field probeaccording to claim 1,wherein all side surfaces P_(i) (i=1, . . . , n)are coated with the coating material.
 3. Near-field probe according toclaim 1,wherein all edges K_(ik) are coated with the coating material.4. Near-field probe according to claim 1,wherein one edge K_(i),kbetween two adjacent coated sides P_(j) and P_(k) (i, k>0) is uncoated.5. Near-field probe according to claim 1,wherein the body K of thepolyhedron probe comprises photoluminescencing material, or that thematerial of the body is doped with photoluminescent centers in a zone ofthe surface including the point.
 6. Near-field probe according to claim1,wherein the body K of the polyhedron probe comprises nonlinear opticalmaterial with high nonlinear optical susceptibilities.
 7. Device foroptical near-field microscopy according to claim 1, comprising saidnear-field probe, anda detector, and a filter mounted upstream of thedetector, and said filter suppressing the transmission of irradiationlight.
 8. Device for inverse photon tunnelling microscopy according toclaim 1, comprising said near-field probe, andan object support, and athin layer of silver or gold with a thickness of about 10 to 100 nm is acomponent of said object support, said layer being almost opaque toirradiation light and serving as a substrate for an object to beexamined.
 9. Device for optical near-field microscopy and simultaneousscanning tunnelling microscopy according to claim 1, comprisingproviding a near-field probe, andan object, and wherein coatings withcoating material and said object are each provided with an electriccontact, so that current flowing between the point and the object can bemeasured.